Electrophoresis systems which employ the zone electrophoresis method of separating proteins, polypeptides, nucleic acids or other organic molecules with electrical charge to determine their quantities and molecular weights are common in the prior art. Sample components of these organic molecules, supported on stabilizing media, are separated by an electric field on the basis of differences in net charge, size and shape. The separation takes place at a constant pH and ionic strength. Polyacrylamide gel, agarose, cellulose or granulated gels are commonly used as stabilizing media, these gels being porous compounds through which the sample components can migrate in an electric field. The electric field applied to the gel causes samples to migrate through the gel.
DNA (deoxyribonucleic acid), for example, which is negatively charged, moves toward the positive electrode; smaller fragments of DNA migrate faster through the gel than do larger fragments. A gradient of DNA sizes is thus established, and the individual size classes may be detected by reacting with ethidium bromide and examining the gel in ultraviolet light. In contrast, proteins may have net negative or positive charges, and therefore migrate unpredictably. For polypeptides, they are first reacted with the detergent sodium dodecyl sulfate (SDS) to cover them with a uniform net negative charge. The resultant complex is then electrophoresed in a gel which also contains SDS. Individual classes of polypeptides are thus separated on the basis of molecular weight--the smaller polypeptides can penetrate the pores in the gel more readily than the larger ones, and a gradient of molecular weights is established. The polypeptides can then be observed by reacting the gels with various protein-specific stains.
These electrophoresis systems can also employ the isoelectric focussing method, a variant of electrophoresis. In this method, a pH gradient is first established electrophoretically by using an isoelectric focussing gel such as a gel containing ampholenes. After the establishment of such a gradient, samples such as polypeptides are then placed on the gel and they migrate to their respective isoelectric points on the pH gradient. Again, the locations of these samples on the gel are observed by using the various protein-specific stains.
Although these systems are satisfactory in their use, they are expensive and composed of many parts. They are also bulky and cumbersome and difficult to transport to remote non-laboratory working sites. Moreover, their time-consuming procedures require approximately three days to produce the laboratory results.